It has served as a model for other pachycephalosaurs, due to the completeness of the excavated remains. From the 1920s to 1945, it was believed to be related to, or even synonomous with, Troodon, due to the similar form of the teeth. This proposal was, however, dispelled after better remains were found.

Anatomy

Stegoceras sported a three inch-thick skull. It was initially proposed that male Stegoceras (and individuals of other pachycephalosaurid species) would ram each other headlong, not unlike contemporary bighorn sheep or musk oxen. It was later suggested that they engaged in flank-butting rather than ramming, a widely evidenced theory. Foremost, the rounded shape of the skull roof would lessen the contacted surface area during head-butting, resulting in glancing blows. Second, pachycephalosaurs could not align their head, neck, and body perfectly horizontally straight (which would be needed to transmit stress) -- it was more likely that they carried their neck in an "S"- or "U"-shaped curve (Stegoceras seemed to carry their spine in a less extreme curve, due to their thick neck muscles). Lastly, the relatively wide width of most pachycephalosaurs would have served to protect vital organs from harm during flank-butting.

When a partial skeleton of Stegoceras was first discovered, it was thought to have gastralia, or belly ribs, not typically found in other ornithischian dinosaurs. They were subsequently found to be ossifiedtendons.